German Rbl.F.36 Gun Optic

Lately I have been finding a few artillery and mortar optics. I like them because they are precision equipment and are quite tactile. The optics viewfinder on this one is a bit different as it has a calculating mechanism for tracking a target traversing the field of view. This one was manufactured by Optische Werke G.Rodenstock in München and has their eso code. It is an Rbl.F.36, which stands for Rundblickfehrnrohr 36. It was used on the Pak-36, 38 & 40 as well as smaller artillery tubes.